In the high speed print production systems, relatively small variations in substrate (e.g., paper) web alignment, paper movement and surface contour can be critical. The same can be said for a print verification system (PVS) that verifies the print on the back-end of a print production system.
Predictable operations and final quality are affected by attributes such as proper web tension, paper to ink-jet head gap, localized deformity (e.g., cockle), flutter and other mechanical anomalies that affect paper. Various means are currently in use to control and detect these aspects of the print or PVS system. Nonetheless, these mechanisms are static (e.g., tension gauge) or limit sensing (e.g., light beam make/break). The nature of the (paper) web, however, is such that simple edge or threshold sensing is insufficient.
Accordingly, an improved detection mechanism is desired.